Rework how UuidAttr, CXXUuidofExpr, and GUID template arguments and constants are represented.
Summary:
Previously, we treated CXXUuidofExpr as quite a special case: it was the
only kind of expression that could be a canonical template argument, it
could be a constant lvalue base object, and so on. In addition, we
represented the UUID value as a string, whose source form we did not
preserve faithfully, and that we partially parsed in multiple different
places.
With this patch, we create an MSGuidDecl object to represent the
implicit object of type 'struct _GUID' created by a UuidAttr. Each
UuidAttr holds a pointer to its 'struct _GUID' and its original
(as-written) UUID string. A non-value-dependent CXXUuidofExpr behaves
like a DeclRefExpr denoting that MSGuidDecl object. We cache an APValue
representation of the GUID on the MSGuidDecl and use it from constant
evaluation where needed.
This allows removing a lot of the special-case logic to handle these
expressions. Unfortunately, many parts of Clang assume there are only
a couple of interesting kinds of ValueDecl, so the total amount of
special-case logic is not really reduced very much.
This fixes a few bugs and issues:
* PR38490: we now support reading from GUID objects returned from
__uuidof during constant evaluation.
* Our Itanium mangling for a non-instantiation-dependent template
argument involving __uuidof no longer depends on which CXXUuidofExpr
template argument we happened to see first.
* We now predeclare ::_GUID, and permit use of __uuidof without
any header inclusion, better matching MSVC's behavior. We do not
predefine ::__s_GUID, though; that seems like a step too far.
* Our IR representation for GUID constants now uses the correct IR type
wherever possible. We will still fall back to using the
{i32, i16, i16, [8 x i8]}
layout if a definition of struct _GUID is not available. This is not
ideal: in principle the two layouts could have different padding.
Reviewers: rnk, jdoerfert
Subscribers: arphaman, cfe-commits, aeubanks
Tags: #clang
Differential Revision: https://reviews.llvm.org/D78171
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 0b3c9b7..af51ae0 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -462,7 +462,7 @@
if (VD->isExternC())
return false;
- // Variables at global scope with non-internal linkage are not mangled.
+ // Variables at global scope with internal linkage are not mangled.
const DeclContext *DC = getEffectiveDeclContext(D);
// Check for extern variable declared locally.
if (DC->isFunctionOrMethod() && D->hasLinkage())
@@ -497,6 +497,10 @@
mangleFunctionEncoding(FD, Context.shouldMangleDeclName(FD));
else if (const VarDecl *VD = dyn_cast<VarDecl>(D))
mangleVariableEncoding(VD);
+ else if (isa<MSGuidDecl>(D))
+ // MSVC appears to mangle GUIDs as if they were variables of type
+ // 'const struct __s_GUID'.
+ Out << "3U__s_GUID@@B";
else
llvm_unreachable("Tried to mangle unexpected NamedDecl!");
}
@@ -893,6 +897,16 @@
break;
}
+ if (const MSGuidDecl *GD = dyn_cast<MSGuidDecl>(ND)) {
+ // Mangle a GUID object as if it were a variable with the corresponding
+ // mangled name.
+ SmallString<sizeof("_GUID_12345678_1234_1234_1234_1234567890ab")> GUID;
+ llvm::raw_svector_ostream GUIDOS(GUID);
+ Context.mangleMSGuidDecl(GD, GUIDOS);
+ mangleSourceName(GUID);
+ break;
+ }
+
// We must have an anonymous struct.
const TagDecl *TD = cast<TagDecl>(ND);
if (const TypedefNameDecl *D = TD->getTypedefNameForAnonDecl()) {
@@ -1364,45 +1378,6 @@
return;
}
- // Look through no-op casts like template parameter substitutions.
- E = E->IgnoreParenNoopCasts(Context.getASTContext());
-
- const CXXUuidofExpr *UE = nullptr;
- if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
- if (UO->getOpcode() == UO_AddrOf)
- UE = dyn_cast<CXXUuidofExpr>(UO->getSubExpr());
- } else
- UE = dyn_cast<CXXUuidofExpr>(E);
-
- if (UE) {
- // If we had to peek through an address-of operator, treat this like we are
- // dealing with a pointer type. Otherwise, treat it like a const reference.
- //
- // N.B. This matches up with the handling of TemplateArgument::Declaration
- // in mangleTemplateArg
- if (UE == E)
- Out << "$E?";
- else
- Out << "$1?";
-
- // This CXXUuidofExpr is mangled as-if it were actually a VarDecl from
- // const __s_GUID _GUID_{lower case UUID with underscores}
- StringRef Uuid = UE->getUuidStr();
- std::string Name = "_GUID_" + Uuid.lower();
- std::replace(Name.begin(), Name.end(), '-', '_');
-
- mangleSourceName(Name);
- // Terminate the whole name with an '@'.
- Out << '@';
- // It's a global variable.
- Out << '3';
- // It's a struct called __s_GUID.
- mangleArtificialTagType(TTK_Struct, "__s_GUID");
- // It's const.
- Out << 'B';
- return;
- }
-
// As bad as this diagnostic is, it's better than crashing.
DiagnosticsEngine &Diags = Context.getDiags();
unsigned DiagID = Diags.getCustomDiagID(